I am going to choose a JMS message broker for a project. It is critical that the JMS server is stable and can handle a high load of messages. I have narrowed down the list to in
HornetQ looks good.
http://www.spec.org/jms2007/results/jms2007.html
JBoss recently redid their entire implementation of Messaging, ala JBoss MQ has been replaced with JBoss Messaging, and now again as "HornetQ". You'll just want to keep that in mind as that above comparison is very dated (not to mention probably biased).
So far, I had a great experience with the community wiki and documentation of Jboss, and it pretty much covers everything. Though, I found quite obvious configuration settings left out in their latest documentations, but I guess this must have been improved since then. For ActiveMQ, I found very little documentation comparing to Jboss.
I have done certain research using MOM with Jboss and GlassFish, but one of the most important impact was the permanent storage if you are going to use any. I think this itself is very important, especially their compatibility, support, documentations.
Take a look at this. Apparently there are certain concern when it comes to persistent storage in ActiveMQ.
http://www.jboss.org/file-access/default/members/jbossmessaging/freezone/docs/userguide-2.0.0.alpha1/html/performance.html#performance.results
JBoss Messaging is now in bug fix mode only, since JBoss / Red Hat has a new Java messaging project called HornetQ.
The web site is here http://hornetq.org
HornetQ boasts extreme performance, a full feature set and ease of use.
You'll find it's performance compared to ActiveMQ is extremely good.
BTW - I am the project lead for JBoss Messaging and HornetQ.
HornetQ 2.0.0.GA is out in the next week.
Feature-by-feature comparisons are all very well, but my experience of ActiveMQ (through various versions over the years) is that it is shockingly buggy, and noone seems inclined to fix those bugs. It's deeply frustrating. Also, the documentation is messy and not properly updated with new versions.
JBossMessaging is relatively feature-light, compared to ActiveMQ, but it's rock-solid, well-documented and reliable. It's also part of JBossAS 5, and RedHat are doing a good job of supporting it.
JBoss Messaging replaces JBoss MQ. Here are Messaging performance data: http://www.jboss.org/community/docs/DOC-10640
JBoss MQ is not scalable at all: http://www.jboss.org/community/docs/DOC-12452